The teams the New York Yankees haven't been able to beat in the American League spent the last two years trading for dominant starting pitchers. For two straight years, the Yankees have been the team that passed on those trades—and eventually, they were the team that didn't win.

Now maybe all that changes.

Now the Yankees have begun the offseason with a deal for James Paxton, a starting pitcher who could be dominant. They've begun to address by far their biggest need, and they've done it without spending the kind of money that would seriously eat into their winter budget. Even Justus Sheffield, the most prominent of the three prospects the Yankees sent to the Seattle Mariners in exchange for Paxton, elicits mixed reactions from rival scouts.

Paxton does, too, but only because he hasn't stayed healthy through his first six seasons in the major leagues.

"Even if he pitches 120 innings this year and next year, he's more valuable to the Yankees in that time than Sheffield," one American League scout said. "If he pitches 160, he's at least a No. 3 starter. At 175, he's a No. 2, and if he makes all his starts, he's a possible ace."

Paxton showed off his dominant stuff in a no-hitter in May in Toronto.Tom Szczerbowski/Getty Images

Paxton pitched 160.1 innings for the Mariners in 2018, easily the most in his big league career. He had a 3.76 ERA and 11.7 strikeouts per nine innings.

"I've seen him just dominate," the scout said.

"He would be at the top of most rotations," another AL scout said.

The only pitchers in the big leagues with 27-plus starts and a higher strikeout rate in 2018 were Chris Sale, Gerrit Cole, Max Scherzer and Justin Verlander, per Baseball Reference. Right behind Paxton were Trevor Bauer, Jacob deGrom, Patrick Corbin and Blake Snell.

That's good company, with four pitchers who have won Cy Young Awards (Scherzer has three) and eight who received Cy Young votes in 2018 (everyone but Paxton). DeGrom and Scherzer finished 1-2 in the National League voting this year; Snell and Verlander finished 1-2 in AL voting.

Cole and Verlander are two big-time starters the Yankees didn't trade for over the last two years. Both went to the Houston Astros, the team the Yankees couldn't beat in the 2017 postseason.

Sale was traded two offseasons ago to the Boston Red Sox, the team that finished ahead of the Yankees in the AL East in 2018 and beat them in the division series, too.

The Paxton trade may have set up the Yankees for a major rotation upgrade that could also include free agent Patrick Corbin.Denis Poroy/Getty Images

Starting pitching was the biggest difference between the Yankees and the Astros in 2017, and between the Yankees and the Red Sox in 2018.

Adding Paxton narrowed that gap. Add Paxton and Corbin, who grew up a Yankees fan and is now a free agent, and the Yankees may have a rotation that can match up with their rivals'.

It doesn't have to be Corbin. The Yankees could sign Dallas Keuchel or J.A. Happ, who are also free agents. They're almost certain to add at least one more starter, but by getting Paxton now at a reasonable cost, they've already given the rotation a needed boost. In Paxton and Luis Severino, they have two starters with top-of-the-rotation stuff, even if neither yet has the ace history Sale brought to the Red Sox or Verlander brought to the Astros.

Paxton made $4.9 million in 2018. He's arbitration-eligible and will get a raise in 2019, but his salary will still be well below what the top free-agent starters can command.

That should leave enough money in the Yankees' budget for them to pursue other players and potentially make this a big winter. Maybe that means adding to the bullpen. Maybe it means going after Marwin Gonzalez, who could fill in for the injured Didi Gregorius at shortstop and has the versatility to move almost anywhere when Gregorius returns.

Or maybe it means going bigger to sign Manny Machado, who would be a Gregorius replacement but also a big addition to the middle of the lineup. Or maybe the Yankees eventually turn to Bryce Harper. Could he play first base and give them the left-handed middle-order bat they still need?

However it works out, Paxton was worth taking a chance on because the potential upside is great. And while he hasn't been durable, Paxton hasn't had the kind of serious elbow or shoulder injuries that would raise more serious concerns.

"I think my best baseball is still to come," Paxton told reporters on a conference call after the trade was announced Monday night.

The Mariners no doubt believe the same about Sheffield, who had a 2.48 ERA in 25 appearances split between Double-A and Triple-A in 2018 and also made three relief appearances with the Yankees. One scout who has seen Sheffield a lot suggested he was overthrowing in 2018 in an effort to get to the big leagues. An executive from another team said some of his scouts believe Sheffield's future will be as a reliever.

While MLB.com had him ranked as the Yankees' top prospect and has him ranked as the 31st-best prospect in all of baseball, none of three scouts contacted by Bleacher Report ranked him that highly. The same goes for pitcher Erik Swanson and outfielder Dom Thompson-Williams, the other two players the Yankees sent to the Mariners.

But trades for prospects are always tough to evaluate at the time, and how well the Mariners did will only become clear over the next several years.

For the Yankees, though, it's easy to say Paxton brings more value than Sheffield right now. Sheffield was unlikely to break into their 2019 rotation, while Paxton joined a group that also includes Severino, Masahiro Tanaka and CC Sabathia, even before they make any other moves.

The Paxton trade by itself won't give them a championship rotation. But as a first step in the middle of November, it was a trade that could lead to a very promising offseason.

Danny Knobler covers Major League Baseball as a national columnist for Bleacher Report.